Electrically conductive fluid treatment elements

ABSTRACT

Fluid treatment elements substantially inhibit electrical charge imbalances and/or build-ups of electrical charges. A fluid treatment element may comprise a multilayer composite including an electrically conductive fibrous matrix, having an upstream side and a downstream side, disposed on a porous substrate, also having an upstream side and a downstream side, which supports the fibrous matrix. The fibrous matrix may include a combination of conductive and nonconductive fibers. The multilayer composite may also include a drainage layer positioned along one of the upstream side of the fibrous matrix and the downstream side of the porous substrate.

This application is a divisional of U.S. patent application Ser. No.11/515,813, filed on Sep. 6, 2006, now U.S. Pat. No. 7,455,768, whichwas a divisional of U.S. patent application Ser. No. 10/130,831, filedon Dec. 5, 2002, now U.S. Pat. No. 7,128,835, which was a National StageApplication of International Application No. PCT/US00/31949, filed onNov. 22, 2000, which claimed the benefit of U.S. Provisional PatentApplication No. 60/202,879 , filed on May 9, 2000, and U.S. ProvisionalPatent Application No. 60/166,991, filed on Nov. 23, 1999.

TECHNICAL FIELD OF THE INVENTION

The present invention relates to fluid treatment elements, particularlyto electrically conductive fluid treatment elements which substantiallyinhibit electrical imbalances and/or electrical charge build ups.

BACKGROUND OF THE INVENTION

A wide variety of elements are used to treat fluids, i.e., gases,liquids, and mixtures of gases and liquids. Examples of fluid treatmentelements include separation elements, such as filter elements andseparator elements, coalescer elements, and mass transfer elements. Theymay be used in a wide variety of ways including to remove one or moresubstances, such as solids, liquids or chemical substances, e.g., aprotein, from a gas or liquid; to concentrate or deplete one or moresubstances in a gas or liquid; to accrete one phase of a fluid, e.g., aliquid discontinuous phase, in another phase of the fluid, e.g., acontinuous liquid or gas phase; or to transfer mass, such as a gaseousor chemical substance, between two fluid streams. In use, any of theseelements may develop an electrical change imbalance or buildup that canpotentially damage the fluid treatment system.

For example, filter elements, in addition to removing contaminants suchas solids from fluids, may remove or add electrons to fluid passingthrough the filter elements, causing an imbalance in electrical chargeor potential between the fluid, the filter element, and/or thesurrounding housing, pipes, and fluid cavities. A gradual buildup ofelectrical charge may eventually lead to a discharge through a path ofleast resistance to, for example, the filter housing, the pipes, or anyother conductive component such as a turbine-bearing cage. Thisdischarge can degrade the fluid or harm the components experiencing adischarge arc. The service life of the fluid, the filter element, andthe system containing the fluid is thus reduced.

Various techniques exist that purport to deal with the accumulation ofcharge and the resulting discharge in fluid treatment systems. Onetechnique is to add conductive additives to the fluid. This techniquecan degrade fluid performance and also requires regular monitoring asthe additive's effectiveness diminishes over time and use.

SUMMARY OF THE INVENTION

The present invention effectively addresses the problems of electricalimbalances and charge accumulation in a variety of ways.

In accordance with an aspect of the invention, a fluid treatment elementfor substantially inhibiting an electrical charge imbalance and/or abuild-up of electrical charge may comprise a multilayer composite. Themultilayer composite may include an electrically conductive fibrousmatrix having a first side and a second side and including a combinationof electrically conductive fibers and electrically nonconductive fibers.The electrically conductive fibers of the electrically conductivefibrous matrix may include electrically conductive polymeric fibers andmay substantially inhibit an electrical charge imbalance and/or abuild-up of electrical charge. The electrically conductive fibers maycomprise less than about 50% by weight of the electrically conductivefibrous matrix and may have diameters of about 10 μm or less. Themultilayer composite may also include a porous substrate for supportingthe electrically conductive fibrous matrix. The porous substrate mayhave a first side and a second side and the second side of theelectrically conductive fibrous matrix may be disposed on the first sideof the porous substrate. The multilayer composite may also include afirst drainage layer positioned on the first side of the electricallyconductive fibrous matrix or the second side of the porous substrate.

Many embodiments of the fluid treatment elements effectively inhibitelectrical imbalance and charge buildup (1) by dissipating the charge toa neutral potential such as ground and/or (2) by preventing the chargefrom accumulating in the filter medium.

For some embodiments, the fluid treatment element may comprise a pleatedmulti-layer composite having interior roots and exterior crests.

For some embodiments, the fluid treatment element may be used in a fluidtreatment assembly having a core or a cage such that the fluid treatmentelement is removably mountable to the core or the cage.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a partially cutaway oblique view of a fluid treatment element.

FIG. 2 is a sectional view of a side seam of a pleated fluid treatmentpack.

FIG. 3 is a partially cutaway oblique view of another fluid treatmentelement.

FIG. 4 is a partially cutaway oblique view of another fluid treatmentelement.

FIG. 5 is a partially cutaway elevation view of another fluid treatmentelement.

FIG. 6 is a partially cutaway elevation view of another fluid treatmentelement.

FIG. 7 is an elevation view of a fluid treatment assembly.

FIG. 8 is a partially cutaway elevation view of another fluid treatmentelement.

DETAILED DESCRIPTION OF EMBODIMENTS

One example of a fluid treatment element is a separation element, suchas a filter element. Accordingly, a fluid treatment pack such as afilter pack comprises first and second conductive layers and a porousfluid treatment medium such as a porous filter medium. The first andsecond conductive layers are preferably electrically connected to eachother, and the filter medium is disposed between them. As a fluid, suchas gas or a liquid or a mixture of gas and liquid, flows through thefilter pack, one or more undesirable substances, e.g., particulatecontaminants may be removed from the fluid by the filter medium. Inaddition, an electrical charge may be transferred between the fluid andthe filter medium. The first and second conductive layers are preferablypositioned in sufficient proximity to the filter medium to offset theelectrical imbalance, for example, by dissipating the charge to aneutral potential, such as ground, or where the first and secondconductive layers are isolated from the neutral potential, by collectingthe charge in the fluid treatment medium and returning the charge to thefluid as the fluid flows through the conductive layers or by preventingthe charge from accumulating in the filter medium. Thus, the conductivelayers may be electrically connected to ground or alternatively, even ifthe filter pack is electrically isolated from the ambient environment,e.g., electrically isolated from a neutral potential such as ground, thefirst and/or second conductive layers may offset all or a substantialportion of the electrical imbalance which may arise in the filtermedium. The fluid treatment medium is thus substantially surrounded byan electrical cage which offsets the electrical imbalance.

As shown in FIG. 1, one example of a fluid treatment pack, such asfilter pack 10, embodying the present invention has a pleated, hollow,generally cylindrical configuration, and fluid preferably flowsoutside-in, or alternatively inside-out, through the filter pack 10. Thepleats may extend generally radially and have a height substantiallyequal to (D-d)/2, where D and d are the outer and inner diameters,respectively, at the crests and roots of the pleats. Alternatively, thepleats may extend in a non-radial direction and have a height greaterthan (D-d)/2. For example, the pleats may lie in a laid-over state asdisclosed in U.S. Pat. No. 5,543,047, which is incorporated by referencein its entirety.

The filter pack 10 preferably comprises a pleated, multi-layer compositehaving a porous upstream drainage layer 11, a porous conductivecushioning layer 12, a permeable or semipermeable filter medium 13, anda porous conductive downstream drainage layer 14. The porous fluidtreatment medium, e.g., the filter medium 13, may comprise a porousfluid treatment matrix such as a filter matrix 15, e.g., a fibrous,including filamentous, layer, and the fiber matrix 15 may be supportedby a porous substrate 16. For example, the fiber matrix 15 may bedry-laid or wet-laid on a porous substrate 16 disposed immediatelydownstream of and in intimate contact, preferably intimate bondedcontact, with the filter matrix 15. The conductive cushioning layer 12and the conductive downstream drainage layer 14 may then comprise thefirst and second conductive layers in this embodiment with the filtermedium 13 disposed between them.

The upstream drainage layer 11 may be fashioned from a wide variety ofmaterials having suitable drainage characteristics. For example, theedgewise flow resistance of the upstream drainage layer is preferablysufficiently low that fluid flowing through the filter pack is welldistributed along the upstream surface of the filter medium from thecrests to the roots of the pleats. The upstream drainage layer may be,for example, in the form of a mesh, e.g., a woven, knitted, extruded, orexpanded mesh; a screen; a netting; or a woven or non-woven sheet. Theupstream drainage layer may be formed of a nonconductive material, suchas glass or ceramic fibers or a nonconductive polymer, or a conductivematerial, e.g., a conductive material such as a metal, carbon, or aconductive polymer, or a nonconductive material that has been treated torender it conductive, such as a carbon or metal coated nonconductiveglass or polymer. In the illustrated embodiment, the upstream drainagelayer 11 preferably comprises a nonconductive extruded polyamide (e.g.,nylon) mesh.

The conductive cushioning layer may be fashioned from any suitablematerial which resists abrasion between the upstream drainage layer 11and the filter matrix 15. For example, the conductive cushioning layer11 may be fashioned as a smooth and, preferably, thin and tough woven ornon-woven sheet which is relatively porous compared to the filter medium13, e.g., the filter matrix 15. The conductive cushioning layer 11 maybe formed from a conductive material, such as a metal, carbon, or aconductive polymer, or from a nonconductive material, such as glassfiber or a nonconductive polymer, which is treated in any suitablemanner to render the cushioning layer conductive. For example, aconductive additive, such as metal, carbon, or conductive polymericparticles or fibers, may be included with the nonconductive material orthe nonconductive material may be coated with a conductive coating, suchas a metal or carbon coating. In the illustrated embodiment, theconductive cushioning layer 12 preferably comprises a conductivenonwoven sheet, such as a carbon-coated polyester nonwoven sheet.

The fibrous filter matrix 15 may be fashioned from a variety of fibrous,including filamentous, materials. For example, the filter matrix 15 maybe fashioned from only nonconductive materials, such as glass fibers,e.g., borosilicate fibers, nonconductive polymeric fibers, includingnon-conductive synthetic polymeric fibers, or ceramic fibers, such asalumina, silica, silicates or quartz. Alternatively, the filter matrix15 may be fashioned from a mixture of nonconductive fibers and aconductive material, e.g., metal, carbon, or conductive polymerparticles or fibers. The term “metal” herein refers to a metal by itselfas well as blends of metals such as alloys. Examples of suitable metalsinclude iron, copper, aluminum, nickel, gold, silver, and alloys thatinclude one or more of metals or conductive materials such as carbon.Examples of alloys include stainless steel, bronze, and brass.

The fibers can have any suitable dimensions. For example, the conductivefibers or the non-conductive fibers can have a diameter of from about 1μm or less to about 100 μm or more, for example, in some embodiments,from about 1 μm to about 10 μm, e.g., from about 1 μm to about 3 μm. Theconductive fibers can be incorporated within the non-conductive fibermatrix in an amount that imparts the desired electrical conductivity tothe filter matrix, for example, less than about 50%, typically up toabout 25% or more, in some embodiments from about 15% to about 25%,e.g., from about 22% to about 25% by weight of the filter matrix.

The filter matrix 15 can be prepared by any suitable method, includingby dry-laying or wet-laying. For example, a slurry containing a mixtureof conductive fibers (e.g., metal fibers) and non-conductive fibers canbe prepared. Alternatively, a slurry of the conductive fiber and aslurry of the non-conductive fiber can be prepared separately and theslurries admitted to a mixing chamber where the slurries are mixed. Theslurries can be prepared in any suitable carrier, e.g., water oralcohol. As the viscosity of the metal fiber is generally higher thanthat of most non-conductive fibers, the viscosity and/or the flow rateof the slurries may be suitably adjusted to obtain the desired metalcontent and uniformity of metal distribution in the filter matrix. Theslurries can also include additives such as binders, e.g., resins, toimprove the bonding of the fibers to one another and/or suspension aidssuch as surfactants or thickeners to stabilize the slurries.

The mixture is processed to form a matrix or web. The matrix can beformed by any suitable method, e.g., by methods known in the productionof non-woven fabrics or webs such as paper. The matrix of conductive andnon-conductive fibers can be laid on a surface, such as a screen, onwhich a matrix can be formed and from which the thus formed matrix canbe later removed. The matrix of conductive and non-conductive fibers canalso be laid on porous support, such as a conductive or non-conductivesubstrate to form a composite filter medium. For example, aforming-machine such as an inclined-wire fourdrinier or a cylinderformer can be employed for forming the matrix. By applying suction orvacuum during the formation of the matrix, one can remove the carrier aswell as adjust the thickness, porosity, or density of the matrix. Thematrix obtained can be subjected to bonding processes, e.g., stitching,needle-felting or calendaring, to better interlock the fibers or toimprove or adjust the strength, flexibility, porosity, density, loft,and/or thickness of the matrix.

The filter matrix 15 may have any of several fluid treatingcharacteristics. For example, the filter matrix or the filter medium mayhave a removal rating in the range from about 0.05, or less to about100μ or more, preferably less than about 25μ, or less than about 5μ orless than about 1μ. The filter matrix or the filter medium may have auniform or graded pore structure, i.e., an upstream region having largerpores and a downstream region having finer pores, and/or may comprise asingle layer or multiple sublayers, each having the same or differentfiltering characteristics. In the illustrated embodiment, the filtermatrix 15 comprises a wet-laid, resin-bonded glass fiber layer.

The porous substrate 16 may be fashioned from a variety of suitablematerials. The filter matrix 15 preferably is laid on the substrate 16,e.g., dry-laid or wet-laid, and is bonded to the substrate 16, e.g.,chemically bonded, solvent bonded, thermally bonded, and/or mechanicallybonded by mechanical entanglement of the fibers of the filter matrix andthe substrate, forming a composite filter medium. The substrate 16 thensupports the filter matrix 15 against the differential pressure acrossthe filter matrix 15. The substrate 16 may be, for example, a mesh,screen, netting, or woven or non-woven sheet that is sufficiently strongto support the filter matrix 15 within the filter pack 10. The poroussubstrate 16, like the upstream drainage layer, may be formed from anonconductive material such as glass or ceramic fibers or anonconductive polymer In the illustrated embodiment, the substrate 16preferably comprises a nonconductive nonwoven sheet, such as apolymeric, e.g., polyester, nonwoven sheet.

The conductive downstream drainage layer 14 functions as a drainagelayer in a manner analogous to the upstream drainage layer 11, exceptthe downstream drainage layer 14 drains filtrate from the downstreamside of the substrate from the crests to the roots of the pleats andinto the interior of the filter pack 10. Consequently, many of thecharacteristics of the upstream drainage layer are applicable to thedownstream drainage layer. Further, the downstream drainage layer mayfunction as a conductive layer. The downstream drainage layer may thencomprise a conductive material, such as a metal, carbon, or a conductivepolymer, or a nonconductive material, such as glass fiber or anonconductive polymer, which is treated in any suitable manner to renderthe downstream drainage layer conductive. A conductive additive, such asmetal, carbon, or conductive polymeric particles or fibers, includingfilaments, may be included with the nonconductive material or thenonconductive material may be coated with a conductive coating, such asa metal or carbon coating. In the illustrated embodiment, the downstreamdrainage layer 14 preferably comprises a carbon-coated polyamide (e.g.,nylon) extruded mesh.

The multi-layer composite may be pleated in any suitable manner andformed into a generally cylindrical filter pack 10, for example, bysealing a longitudinal side seam. The filter pack 10 may be incorporatedinto a filter element 21 in a variety of ways. For example, the ends ofthe filter pack 10 may be joined to opposite end caps 22, 23 in anysuitable manner, such as melt bonding, adhesive bonding, or spinbonding. One of the end caps may be blind and the other may be open, orboth end caps may be open. A cage (not shown) may be disposed around theexterior of the filter pack 10 and/or a core 24 may be disposed aroundthe interior of the filter pack 10. Further, a wrap member 25 may bedisposed around the exterior of the filter pack 10. U.S. Pat. No.5,252,207, which is incorporated herein by reference in its entirety,discloses various examples of a wrap member and a wrapped filterelement. The end caps, the core, the cage and the wrap member may beformed of either a conductive material, such as metal or a conductivepolymer, or alternatively a nonconductive material, such as anonconductive polymer.

The conductive layers, such as the conductive cushioning layer 12 andthe conductive downstream drainage layer 14, may be electricallyconnected to each other in a variety of ways. For example, they may beelectrically connected at the longitudinal side seam of the filter pack10. In one embodiment, the edge(s) of at least one, or both, of theconductive layers, e.g., the conductive cushioning layer 12 and theconductive downstream drainage layer 14 extend beyond the edges of theother layers at the side seam and are brought into contact with theother conductive layer. For example, as shown in FIG. 2, the edge of theconductive cushioning layer 12 at the side seam may extend beyond theedges of the other layers and may be folded back into the composite incontact with the conductive downstream drainage layer 14. A sealant 26may then be applied to the side seam, joining and sealing the side seamwith the conductive cushioning layer 12 in electrical contact with theconductive downstream drainage layer 14.

Alternatively or additionally, the first and second conductive layersmay be electrically coupled to each other in any other suitable manner.For example, the side seam sealant may be a conductive sealant, such asa conductive resin or a nonconductive resin having a conductiveadditive. The conductive sealant may be applied to the edges of themulti-layer composite in a manner which allows the conductive sealant toelectrically connect the first and second conductive layers, e.g., theconductive cushioning layer 12 and the conductive downstream drainagelayer 14, at the side seam. For example, the edges of the layers of thecomposite may be coextensive, and the conductive sealant may penetratethe porous layers and, thereby, join and seal them as well aselectrically connect the first and second conductive layers.Alternatively, the side seal may be formed by fusion bonding, e.g.,sonic welding, the edges of the layers, e.g., without the addition of aseparate sealant. Fusion bonding effectively melts the edges of thelayers resulting in a molten mass which may penetrate any interveninglayers and, thereby join and seal them as well as electrically connectthe first and second conductive layers. Where one or more of the layersof the composite material are formed from a conductive material, e.g., aconductive polymer, the melted edge of the conductive material serves asa sealant which can join and seal the layers of the composite as well aselectrically connect the first and second conductive layers.

As another example, electrical connectors, such as conductive staples orconductive threads may be inserted into the edges of the compositematerial at the side seam. The conductive connectors may thenmechanically join the layers of the multi-layer composite andelectrically connect the first and second conductive layers at the sideseam.

Further, the first and second conductive layers may be electricallyconnected through the intervening layers. For example, the filter matrix15 may comprise conductive fibers including conductive filaments, or amixture of conductive and nonconductive fibers and/or the substrate maycomprise conductive material. The conductive cushioning layer 12 and theconductive downstream drainage layer 14 may then be electricallyconnected via the conductive fibers in the filter matrix 15 and theconductive substrate 16 across the entire area of the filter medium 13.

Alternatively or additionally, the first and second conductive layersmay be electrically connected at the ends of the filter pack 10. Forexample, prior to bonding the end caps 22, 23 to the ends of the filterpack 10, the edges of one or both of the conductive layers at the endsof the filter pack 10 may be brought into contact with one another in amanner analogous to that previously described with respect to the edgesat the side seam. Also, a conductive bonding agent, such as a conductiveadhesive, may be used to bond the ends of the filter pack 10 to the endcaps 22, 23, electrically connecting the edges of the conductive layersat the end caps 22, 23 in a manner analogous to that previouslydescribed with respect to the conductive sealant and the edges of theconductive layer at the side seam.

Further, the first and second conductive layers may be electricallycoupled via a conductive end cap, e.g., a metal end cap or an end capformed from a conductive polymer, including a nonconductive polymerhaving a conductive additive. For example, the edges of the conductivelayers at the ends of the filter pack 10 may extend beyond the edges ofthe other layers of the composite and may be folded to lie flat againstthe end caps 22, 23. Also, the end caps 22, 23 may be joined to the endsof the filter pack 10, e.g., with a conductive adhesive. Or, the ends ofthe filter pack 10, with or without the edges of the conductive layersextending beyond the edges of the other layers, may be inserted into amolten portion of each end cap comprising a conductive polymer. Themolten conductive polymer may then wick into the ends of the fluidtreatment pack 10 and, once solidified, join and seal the ends of thefilter pack 10 to the end caps 22, 23 as well as electrically connectthe first and second conductive layers. With the first and secondconductive layers electrically connected to each other, the filtermedium is substantially surrounded with an electrical cage.

While the embodiment illustrated in FIGS. 1 and 2 has been describedwith reference to a fluid treatment pack 10 comprising a conductivecushioning layer 12 as a first conductive layer, e.g., an upstreamconductive layer; a conductive drainage layer 14 as a second conductivelayer, e.g., a downstream conductive layer; and a fibrous fluidtreatment matrix 15 dry-laid or wet-laid on a porous substrate 16, theinvention is not limited to this embodiment. For example, the upstreamconductive layer may alternatively be a conductive upstream drainagelayer or an additional conductive layer which does not function aseither a drainage layer or a cushioning layer. Thus, the cushioninglayer such as the conductive cushioning layer 12 may be eliminatedentirely, and the fluid treatment pack may then comprise a conductiveupstream drainage layer as the upstream conductive layer. Or theupstream conductive layer may be an additional layer which is conductiveand which is positioned upstream of the fluid treatment medium with theupstream drainage layer or with both the upstream drainage layer and theupstream cushioning layer, either or both of which may be conductive ornonconductive.

Further, the downstream conductive layer may be a conductive downstreamcushioning layer or the substrate may be conductive. The conductivesubstrate may be formed from a conductive material, such as metal,carbon or a conductive polymer or from a nonconductive material which istreated in any suitable manner to render the substrate conductive. Forexample, a conductive additive, such as metal, carbon or conductivepolymeric particles or fibers, including filaments, may be included inthe nonconductive material or the nonconductive material may be coatedwith a conductive coating such as metal or carbon coating. Or, thedownstream conductive layer may be an additional layer which isconductive and which does not function as either a drainage layer or acushioning layer. The additional layer may be disposed downstream of thefluid treatment medium with either the downstream cushioning layer orthe downstream drainage layer or with both the downstream drainage layerand the downstream cushioning layer, either or both of which may beconductive or nonconductive.

Further, the fluid treatment medium need not comprise a fibrous matrix12. Rather, the fluid treatment medium may comprise any of a widevariety of porous separation media. For example, the fluid treatmentmedium may comprise a supported or unsupported porous membrane,including a permeable or semipermeable polymeric membrane, such as apolymeric membrane formed from a nonconductive polymer. Alternatively,the fluid treatment medium may comprise a screen or an open-celled foamformed from a conductive or nonconductive material.

The fluid treatment element may be placed in the housing (not shown) ofa fluid treatment assembly such as a filter assembly. In one preferredembodiment, the first and second conductive layers are electricallyconnected to each other. Further, the fluid treatment element mayinclude an electrical contact, and the first and second conductivelayers may be electrically coupled to the electrical contact. Theelectrical contact may preferably comprise any conductive portion of thefluid treatment element which is electrically coupled to the conductivelayers and is arranged to contact a neutral potential, e.g., ground.Preferably, the electrical contact may be coupled to the neutralpotential through the housing or any other conductive portion of thefluid treatment assembly. For example, the electrical contact may be aconductive portion of a conductive end cap that is electrically coupledto the conductive layers of the fluid treatment element, e.g., directlyor via a conductive bonding agent, and is also electrically coupled to aconductive portion of the housing. Alternatively or additionally, theelectrical contact may be a portion of a conductive core that iselectrically coupled to the first and second conductive layers and iselectrically connected to a conductive portion of the housing, e.g., astool, a spider, or a tie rod of the housing. Alternatively oradditionally, the electrical contact may comprise one or more additionalconductive components such as a conductive wire, strap, spring or seal,e.g., a conductive O-ring or gasket that is electrically coupled to theconductive layers, e.g., directly or via a conductive bonding agentand/or a conductive end cap, and to a conductive portion of the housing.

While not being bound by any particular theory of operation, it isbelieved that as the fluid passes through the filter medium, inparticular as a nonconductive or conductive fluid passes through thefilter medium, electrical charge may be transferred between the filtermedium and the fluid. The first and second conductive layers comprisingthe conductive upstream cushioning layer and the conductive downstreamdrainage layer are positioned in sufficiently close proximity to thefluid treatment medium to offset any electrical imbalance. Additionally,by coupling the electrical contact to a neutral potential and byelectrically connecting the conductive layers to each other and theelectrical contact, any charge build-up in the filter medium or fluidmay be substantially inhibited.

In another preferred embodiment the first and second conductive layersare electrically connected and are also preferably isolated, e.g.,insulated, from a neutral potential, such as ground. The first andsecond conductive layers may be isolated in any suitable manner. Forexample, the end caps as well as the upstream drainage layer and thedownstream drainage layer may be fashioned from a nonconductivematerial, preventing any electrical connection between the first andsecond conductive layers and the housing and, thereby to ground. Asanother example, if the fluid treatment element includes a cage and acore, the cage and the core as well as the end caps may be fashionedfrom a nonconductive material, again preventing any electricalconnection between the first and second conductive layers and ground. Inyet another example, if the exterior and interior of the fluid treatmentelement are spaced from the conductive portions of the housing, thenonly the end caps may be fashioned from a nonconductive material. Forany of these examples, if the ends of the fluid treatment pack areelectrically insulated from the end caps, e.g., by a nonconductiveadhesive, then the end caps may also be fashioned from a conductivematerial.

In a preferred mode of operation, a fluid to be treated is directedthrough the housing of the fluid treatment assembly and through thefluid treatment element, e.g., outside-in through the filter element 21in a dead-end mode of filtration. The fluid is distributed by theupstream drainage layer 11 along the upstream surface of the conductivecushioning layer 12 and, hence, to the upstream surface of the fluidtreatment medium 13, e.g., the upstream surface of the filter matrix 15.The fluid then passes through the fluid treatment medium 13, e.g.,through the filter matrix 15, depositing undesirable substances such asparticulates on or within the filter matrix 15. The fluid then passesthrough the conductive substrate 16 and drains along the downstreamdrainage layer 14 through the perforated core 24 to the interior of thefluid treatment pack 10.

While not being bound by any particular theory of operation, it isbelieved that as the fluid passes through the fluid treatment medium 13,in particular, as a conductive or nonconductive fluid passes through thefilter medium, electrical charge may be transferred between the medium13, e.g., the fluid treatment matrix 15, and the fluid. The first andsecond conductive layers 12, 14 are positioned in sufficiently closeproximity to the fluid treatment matrix 15 to offset the electricalimbalance, e.g., to gather the electrical charge from the fluidtreatment matrix 15 and return the charge to the fluid and/or to preventthe charge from accumulating in the fluid treatment matrix 15. Forexample, one or both of the first and second conductive layers may beimmediately adjacent to and in face-to-face contact with the fluidtreatment medium. This configuration is preferred because it enhancesthe electrical coupling between the fluid treatment medium and theconductive layer(s) over the entire surface area of the fluid treatmentmedium. Alternatively, one or more nonconductive layers may beinterposed between the fluid treatment medium and each of the first andsecond conductive layers as long as the first and/or second conductivelayers are sufficiently close to the fluid treatment medium to inhibitelectrical imbalance and/or charge build-up through the interveninglayer. Electrical imbalance and/or charge build-up in the fluidtreatment medium and/or the fluid is thus substantially reduced. Theporosity of both conductive layers or at least the downstream conductivelayer is preferably arranged to provide sufficient contact between thefluid and the conductive layer to facilitate offsetting the electricalimbalance as the fluid flows through the conductive layers. For example,the nominal pore size one or both of the conductive layers may be lessthan about 500% or less than about 250% or less than about 100%.However, the pore size of each conductive layer is preferably largeenough that no substantial pressure drop occurs as the fluid flowsthrough the conductive layer. For example, the pressure drop through thedownstream conductive layer is preferably no greater than about 5% orpreferably no greater than about 1% of the pressure drop through thefluid treatment pack.

While the embodiment illustrated in FIGS. 1 and 2 has been describedwith reference to a generally cylindrical, pleated fluid treatmentelement, such as a filter element arranged for dead-end filtration, theinvention is not limited to this embodiment. For example, the fluidtreatment element may have a box-like configuration and/or the fluidtreatment pack may include micro-pleats and macro-pleats. Severalexamples of a fluid treatment element having a box-like configurationand micro- and macro-pleats are disclosed in U.S. Pat. No. 5,098,767,which is incorporated by reference in its entirety. As another example,the fluid treatment pack may be spirally-wound rather than pleated, anda fluid treatment element including pleated or spirally-wound pack maybe arranged for cross flow separation, e.g., cross flow filtration.Several examples of a fluid treatment element including a pleated orspirally-wound fluid treatment pack being arranged for cross flowseparation and/or mass transfer are disclosed in InternationalPublication No. WO 00-13767, which is incorporated by reference in itsentirety.

In accordance with a second aspect of the invention, a fluid treatmentpack comprises a pleated multi-layer composite having interior roots andexterior crests. The multi-layer composite includes a porous fluidtreatment medium and at least one conductive layer electrically coupledto the porous medium to transfer charge between porous medium and theconductive layer. The fluid treatment pack may be removably mountable toa conductive perforated core and the conductive layer may comprise theinterior surface of the fluid treatment pack including the interiorsurface at the roots. Alternatively or additionally, the fluid treatmentpack may be removably mountable to a conductive perforated cage and theconductive layer may comprise the exterior surface of the fluidtreatment pack including the exterior surface at the crests. The pleatsmay be respectively dimensioned to enhance the electrical connectionbetween the conductive layer and the core and/or the cage, e.g., byallowing the roots and/or the crests to press against the core and/orcage. As fluid flows through the fluid treatment pack, the fluid may betreated, e.g., undesirable substances, such as particulates, may beremoved from the fluid. With the porous medium electrically coupled tothe conductive layer and with the conductive layer electrically coupledto the core and/or cage, a substantial portion of any electrical chargein the porous fluid treatment medium and/or fluid may be dissipated viathe conductive layer and the conductive core and/or cage to a neutralpotential, such as ground.

In one preferred embodiment, a fluid treatment pack comprises amulti-layer composite removably mountable to a conductive perforatedcore. The multi-layer composite preferably includes a non-conductiveupstream drainage layer, an upstream conductive cushioning layer, aporous filter matrix bonded to a conductive substrate, and a conductivedownstream drainage layer. The conductive layers are preferablyelectrically connected via a longitudinal side seam, for example byfusion bonding the conductive layers at the side seam. Further, themulti-layer composite is preferably pleated and the pleats aredimensioned to allow the roots to press against the core and provide anelectrical connection at the roots which comprises contact between theconductive downstream drainage layer and the core.

As shown in FIG. 3, one example of a fluid treatment pack, e.g., afilter pack 40, embodying the present invention comprises a pleated,multi-layer composite having a hollow, generally cylindricalconfiguration. The multi-layer composite may comprise a porous upstreamdrainage layer 41, a porous conductive cushioning layer 42, a fluidtreatment medium, such as a permeable or semipermeable filter medium 43,and a porous conductive downstream drainage layer 44, which includes theinterior surface of the fluid treatment pack 40. The fluid treatmentmedium 43 may comprise a fluid treatment matrix 45, e.g., a fibrous,including filamentous, layer, and the fluid treatment matrix 45 may bedry-laid or wet-laid on and bonded to a porous conductive substrate 46.The porous conductive substrate 46 is preferably disposed immediatelydownstream of and in intimate bonded contact with the fluid treatmentmatrix 45, and the conductive downstream drainage layer 46, which maycomprise the conductive layer in this embodiment of this second aspectof the invention, is disposed immediately downstream of and inface-to-face contact with the conductive substrate 46. Similarly, theconductive cushioning layer 42 is disposed immediately upstream of andin face-to-face contact with the fluid treatment matrix 45, and theupstream drainage layer 41, which may also comprise the conductive layerin this embodiment of the invention, is disposed immediately upstream ofand in face-to-face contact with the conductive cushioning layer 42.

Many of the properties of the drainage layers, the cushioning layers,and the fluid treatment media may be similar to those previouslydescribed with the respect to the embodiment shown in FIG. 1. However,the upstream and downstream drainage layers in the embodiment shown inFIG. 3 are preferably fashioned from any of a variety of suitableconductive materials to provide a conductive interior surface of thefluid treatment pack, e.g., at the roots of the pleats, and a conductiveexterior surface, e.g., at the crests of the pleats. For example, theconductive drainage layers may be fashioned from a conductive material,such as a metal, carbon, or a conductive polymer, or from anonconductive material, such as glass fiber or a nonconductive polymer,which is treated in any suitable manner to render the downstreamdrainage layer conductive. A conductive additive, such as metal, carbon,or a conductive polymeric particles or fibers, including filaments, maybe included with the nonconductive material or the nonconductivematerial may be coated with a conductive coating, such as a metal orcarbon coating. In the embodiment illustrated in FIG. 3, the upstreamand downstream drainage layers 41, 44 preferably comprise a conductive,carbon-coated polyamide (e.g., nylon) extruded mesh; the conductivecushioning layer 42 and the conductive substrate 46 preferably comprisea conductive carbon-coated polyester nonwoven sheet; and the fluidtreatment matrix 45 preferably comprises a filter matrix of wet-laid,resin-bonded glass fibers.

The multi-layer composite may be pleated in any suitable manner andformed into the generally cylindrical fluid treatment pack, such as afilter pack 40, for example, by sealing a longitudinal side seam. Thepleats may extend generally radially and have a height substantiallyequal to (D-d)/2, or the pleats may extend non-radially and have aheight greater than (D-d)/2. The fluid treatment pack 40 may beincorporated in a fluid treatment element 51 in a variety of ways, aspreviously described with respect to the embodiment of FIG. 1. Forexample, the ends of the fluid treatment pack 40 may be joined toopposite open or blind end caps 52, 53, and the end caps may be formedfrom a conductive material or a nonconductive material. A wrap member 54may be disposed around the exterior of the fluid treatment pack 40. Inthe illustrated embodiment, the end caps 52, 53, the wrap member 54 andany adhesive bonding material or sealant are all preferably conductive.

In accordance with this second aspect of the invention, the fluidtreatment element preferably does not include at least one of a core anda cage. Rather, the core and/or the cage may be mounted and electricallyconnected to the housing of a fluid treatment assembly, and the housingmay, in turn, be electrically connected to a neutral potential such asground. The fluid treatment element is preferably removably mounted tothe core and/or the cage. In the illustrated embodiment, the fluidtreatment element 51 may be removably mountable to a core, the corebeing attached to the housing of a fluid treatment assembly (not shown),which, in turn, is connected to ground. U.S. Pat. No. 5,476,585, whichis incorporated by reference in its entirety, discloses various examplesof coreless fluid treatment elements. However, in embodiments of thissecond aspect of the invention, the pleats are preferably dimensioned tocontact the core.

The conductive layer, such as the conductive upstream drainage layer 41and/or the conductive downstream drainage layer 44, and the fluidtreatment medium, such as the fibrous fluid treatment matrix 45, may beelectrically coupled to each other in any suitable manner. For example,in the embodiment of FIG. 3, the fibrous filter matrix 45, whetherconductive or nonconductive, is in sufficiently close proximity to,preferably immediately adjacent to and in face-to-face contact with, theconductive cushioning layer 42 and the conductive substrate 46 totransfer electrical charge between them across the entire area of thefilter medium. The conductive cushioning layer 42 and/or the conductivesubstrate 46, in turn, may each be electrically connected to theconductive upstream drainage layer 41 and/or the conductive downstreamdrainage layer 44, as well as the conductive cushioning layer 42 and theupstream drainage layer, in a variety of ways, as previously describedwith respect to the embodiment shown in FIG. 1. For example, theconductive substrate 46 and the conductive downstream drainage layer 44may be immediately adjacent one another and in intimate electricalcontact with one another over the entire surface area of the conductivedownstream drainage layer 44. Alternately, or additionally, theconductive layer, e.g., the conductive upstream and/or downstreamdrainage layer, may be electrically connected to one or more of theother conductive layers, including, for example, a conductive fluidtreatment medium or fluid treatment matrix, a conductive substrate, aconductive cushioning layer, and/or a conductive drainage layer, at theside seam, at the ends of the fluid treatment pack, via conductive endcaps, or via conductive intervening layers, all as previously describedwith respect to the previous embodiments.

While the embodiment illustrated in FIG. 3 has been described withreference to a coreless fluid treatment pack such as a filter pack 40comprising a fibrous filter matrix 45 dry-laid or wet-laid on aconductive substrate 46 and conductive upstream and/or downstreamdrainage layers 41, 44 as the conductive layer(s) electrically coupledto the fibrous matrix 45, the invention is not limited to thisembodiment. For example, one or more conductive or non-conductive layersmay be added to the fluid treatment pack. A conductive layer whichfunctions neither as a cushioning layer nor a drainage layer may beadded to the fluid treatment pack upstream or downstream of the fluidtreatment medium. A conductive or nonconductive downstream cushioninglayer may be disposed between the conductive substrate and theconductive downstream drainage layer, and the conductive downstreamdrainage layer may be connected to the conductive upstream cushioninglayer at the side seam or at the ends of the fluid treatment pack andmay be connected to the conductive substrate at the side seam, at theends of the pack, or via face-to-face contact through the interveningdownstream cushioning layer. As another example, one or more of thelayers may be fashioned from non-conductive material or may beeliminated entirely. The upstream cushioning layer or the substrate maybe non-conductive or eliminated entirely, or both may be non-conductiveor eliminated and the fluid treatment medium may be fashioned from aconductive material and electrically connected to the conductivedownstream drainage layer, e.g., at the side seam or the ends of thepack. The conductive downstream drainage layer may be eliminated and theconductive substrate may comprise the conductive layer including theinterior surface of the pack and electrically coupled to the fibrousmatrix.

Further, the fluid treatment element may include a core, eitherconductive or nonconductive, but may be cageless, the cage beingconnected to the housing of the fluid treatment assembly andelectrically connected via the housing to a neutral potential such asground. The fluid treatment pack may then include a conductive layer,such as a conductive upstream drainage layer, having a conductiveexterior surface which connects to the cage directly or indirectlythrough a conductive wrap member. The conductive layer, e.g., theconductive upstream drainage layer, may be electrically coupled to theporous fluid treatment medium or matrix in any suitable manner, e.g., bybeing immediately adjacent to and in face-to-face contact with theporous medium or matrix, via conductive intervening layers, such as aconductive upstream cushioning layer, or via a connection at the sideseam or the ends of the fluid treatment pack to the cushioning layers,the porous medium or matrix, the substrate, or the downstream drainagelayer.

Further, the porous fluid treatment medium need not comprise a fibrousmatrix. Rather, the porous medium may comprise any of a wide variety ofporous separation media. For example, the porous medium may comprise asupported or unsupported porous membrane, including a permeable orsemipermeable polymeric membrane, such as a polymeric membrane formedfrom a nonconductive polymer. Alternatively, the porous medium maycomprise a screen or an open-celled foam formed from a conductive ornonconductive material.

In a preferred mode of operation, a fluid treatment element such as afilter element 51 is mounted over a conductive perforated core of thehousing of a fluid treatment assembly (not shown) through an open endcap. The pleats of the fluid treatment pack 40 are dimensioned toprovide an electrical connection or contact between the interior surfaceof the conductive layer, e.g., the conductive downstream drainage layer44, at the roots of the pleats and the conductive core. Alternatively oradditionally, the fluid treatment element may be mounted within aconductive cage and the pleats of the fluid treatment pack may bedimensioned to provide an electrical connection or contact between theexterior surface of the conductive layer, e.g., a conductive upstreamdrainage layer, at the crests of the pleats and the conductive cage,either directly or indirectly through a conductive wrap. A fluid to betreated, e.g., filtered, is directed through the housing of the fluidtreatment assembly and preferably outside-in but alternativelyinside-out through the fluid treatment element, e.g., through the filterelement 51 in a dead-end mode of filtration. The fluid is distributed bythe upstream drainage layer 41 along the upstream surface of theconductive cushioning layer 42 and, hence, to the upstream surface ofthe fluid treatment medium 43, e.g., the upstream surface of fibrousmatrix 45. The fluid then passes through the fluid treatment medium 43,e.g., through the fibrous filter matrix 45, depositing undesirablesubstances such as particulates on or within the filter matrix 45. Thefluid then passes through the conductive substrate 46 and drains alongthe conductive downstream drainage layer 44 and through the perforatedcore to the interior of the core, from which the fluid exits thehousing.

While not being bound by any particular theory of operation, it isbelieved that as the fluid passes through the fluid treatment medium, inparticular as a conductive or non-conductive fluid passes through a thefluid treatment medium, such as the fluid treatment matrix 45,electrical charge may be transferred between the fluid treatment medium,e.g., the fibrous matrix 45, and the fluid. By providing electricalcontact between the grounded core or cage and the interior or exteriorsurface of the conductive layer and by electrically coupling theconductive layer to the fluid treatment medium, the electrical imbalanceis substantially offset and charge buildup in either the fluid treatmentmedium or the fluid is substantially inhibited. Once the fluid treatmentelement becomes sufficiently fouled, it may be removed from the core orcage and a cleaned or new fluid treatment element may be remounted tothe core or cage.

In a preferred embodiment of this second aspect of the invention, theonly electrical connection between the neutral potential such as groundand the fluid treatment pack is via the electrical contact between theinterior surface of the conductive layer(s) and the core and/or theexterior surface of the conductive layer(s) and the cage. The surfacearea of the contact between the interior and/or exterior surface of theconductive layer(s) at the roots and/or crests of the pleats and thecore and/or cage is very large and, therefore, provides a highlyeffective electrical contact. The end caps may thus be formed from anon-conductive material such as a non-conductive polymeric material. Noadditional grounding connections, such as grounding straps, groundingsprings, or conductive O-ring seals need be provided, simplifying boththe construction of the fluid treatment element and the retrofitting ofthe existing fluid treatment assemblies with fluid treatment elementsembodying this second aspect of the invention. Alternatively, the fluidtreatment element may be electrically coupled to ground via any of thesevarious other grounding connections in addition to the electricalconnection between the conductive layer(s) at the roots and/or crests ofthe pleats and the core and/or cage.

While the embodiment illustrated in FIG. 3 has been described withreference to a generally cylindrical, pleated fluid treatment elementsuch as a pleated filter element arranged for dead-end filtration, theinvention is not limited to this embodiment. Many of the alternativessuggested with respect to the embodiment shown in FIGS. 1 and 2 areapplicable to the embodiment shown in FIG. 3. For example, the fluidtreatment element may include a pleated pack arranged for cross-flowseparation or mass transfer.

In accordance with a third aspect of the invention, a fluid treatmentelement comprises a fluid treatment pack which includes a fibrous matrixsupported by a conductive substrate. Preferably, the fibrous matrix isdry laid or wet laid on and bonded to the conductive substrate. Thefluid treatment element further comprises an electrical contact which iselectrically coupled to the conductive substrate. The electrical contactof the fluid treatment element is also arranged to be connected to aconductive portion of a fluid treatment assembly, e.g., the housing ofthe assembly, which, in turn, is connected to a neutral potential, suchas ground. As the fluid flows through the fluid treatment assembly and,hence, through the fluid treatment element, the fluid is treated by thefibrous matrix. In addition, electrical charge may be transferredbetween the fluid and the fibrous matrix. Because the conductivesubstrate is bonded to the fibrous matrix, it is closely electricallycoupled to the fibrous matrix. Consequently, a substantial portion ofany charge imbalance which may arise in the fibrous matrix and/or thefluid can be substantially offset by the connection to the neutralpotential via a conductive path including the conductive substrate andthe electrical contact of the fluid treatment element and the conductiveportion of the fluid treatment assembly.

As shown in FIG. 4, one example of a fluid treatment element, e.g., afilter element 70, embodying the present invention comprises a fluidtreatment pack, such as a filter pack 71, bonded to open and blind endcaps 72, 73 at opposite ends of the filter pack 71. The pack 71 issupported by a core 74 and a cage 75 along the interior and exteriorsurfaces of the pack 71. The core 74 and the cage 75 are preferablypermanently connected to the fluid treatment element 70, although thefluid treatment element may be coreless or cageless. In the illustratedembodiment, the end caps 72, 73, the core 74, the cage 75 and anyadhesive bonding material or sealant are all preferably conductive.

The fluid treatment pack, e.g., the filter pack 71, may comprise apleated, multi-layer composite having a hollow, generally cylindricalconfiguration. The multi-layer composite may be pleated in any suitablemanner and formed into the generally cylindrical pack, for example, bysealing a longitudinal side seam. The pleats may extend generallyradially and have a height substantially equal to (D-d)/2, or the pleatsmay extend nonradially and have a height greater than (D-d)/2.

The pleated multi-layer composite may comprise a porous conductiveupstream drainage layer 80, a porous conductive upstream cushioninglayer 81, fluid treatment medium, such as a filter medium 82, includinga fibrous matrix, such as a fibrous filter matrix 83, dry-laid orwet-laid on and bonded to a porous conductive substrate 84, and a porousconductive downstream drainage layer. Many of the properties of thedrainage layers and the cushioning layers may be similar to thosepreviously described with respect to the embodiments shown in FIGS. 1-3.

However, the fluid treatment medium, e.g., the filter medium 82, maycomprise a fibrous fluid treatment matrix 83 supported by the conductivesubstrate 84. Preferably the fibrous fluid treatment matrix 83 is laidon and bonded to the conductive substrate 84. The fibrous matrix 83 maybe fashioned from a variety of fibrous, including filamentous, materialsand may be formed from only nonconductive materials, from conductivematerials, or from a mixture of conductive and nonconductive materials.The conductive substrate 84 may be fashioned from a mesh, screen,netting, or woven or non-woven sheet and may be formed from a conductivematerial or a nonconductive material which is treated in any suitablemanner to render the substrate conductive. The fibrous matrix 83 ispreferably laid on the conductive substrate 84, e.g., dry-laid orwet-laid, and is bonded to the conductive substrate 84, e.g., chemicallybonded, solvent bonded, thermally bonded, and/or mechanically bonded bymechanically entanglement of the fibers of the fibrous matrix 83 and thesubstrate 84, thereby forming a composite fluid treatment medium 82.Many preferred composite media comprising a filter matrix and aconductive substrate are disclosed, for example, in U.S. ProvisionalPatent Application No. 60/166,990 of Joseph Adiletta, Leonard Bensch,Kenneth Williamson, and Ronald Hundley, entitled Porous Media ForDissipating Electrical Charge and the PCT application of JosephAdiletta, Leonard Bensch, Kenneth Williamson, and Ronald Hundley,entitled Porous Media For Dissipating Electrical Charge filedconcurrently with this application, which are incorporated by referencein their entirety. In the illustrated embodiment, the conductivesubstrate 84 preferably comprises a conductive non-woven sheet, such asa carbon coated polyester non-woven sheet, and the fibrous matrix 83preferably comprises a wet-laid, resin-bonded glass fiber layer. Theconductive substrate and the electrical contact may be electricallycoupled in a wide variety of ways, including, any of the previouslydescribed electrical connections at the side seam, at the ends of thefluid treatment pack, or via intervening conductive layers.

The electrical contact preferably comprises any conductive portion ofthe fluid treatment element which is electrically coupled to theconductive layer and is arranged to contact a conductive portion of thefluid treatment assembly. For example, the electrical contact may be anyconductive portion of the fluid treatment pack 71 (e.g., the interiorsurface or the exterior surface), the end caps 72, 73, the core 74, andthe cage 75 which is electrically connected to the conductive substrate84 and is arranged to contact a conductive portion of the fluidtreatment assembly. In particular, the electrical contact 86 maypreferably comprise a conductive portion of the open end cap 73 or thecore 74 which may be mounted to and electrically contact a conductivefitting of the housing (not shown) which, in turn, is connected to aneutral potential such as ground.

While the embodiment illustrated in FIG. 4 has been described withreference to a fluid treatment element, such as a filter element 70,which has a core 74 and a cage 75 and which includes several conductivecomponents, the invention is not limited to this embodiment. Forexample, one or more conductive or nonconductive layers, such as aconductive or nonconductive downstream cushioning layer or a conductivelayer which functions neither as a cushioning layer nor a drainagelayer, may be added to the fluid treatment pack. As another example, oneor more or all of the drainage layers, cushioning layers, and additionallayers may be fashioned from a nonconductive material. The conductivesubstrate may, for example, then be connected to the electrical contactvia a conductive end cap. As still another example, one or more of thecushioning layers, the drainage layers, or the additional layers, suchas the upstream cushioning layer or the downstream drainage layer may beeliminated entirely.

Further, the fluid treatment element may be cageless and/or coreless.The electrical contact may then comprise the exterior surface and/or theinterior surface of the fluid treatment pack which contacts the cageand/or the core and is thereby electrically coupled to a neutralpotential such as ground. Or the cage, the core, or both the cage andcore may be fashioned from a nonconductive material. The electricalcontact may then comprise a surface of a conductive end cap which isarranged to electrically contact a conductive portion of the housing. Orthe end caps or the adhesive connecting the ends of the fluid treatmentelement to the end caps may be nonconductive. The electrical contact maythen comprise a surface of a conductive cage or core which iselectrically coupled to the conductive substrate in any suitable manner.The conductive cage or core may then be electrically connected to aconductive portion of the fluid treatment assembly in a wide variety ofways, e.g., via a conductive strap or wire or spring connecting the cageor the core to the housing.

In a preferred mode of operation, a fluid treatment element, such as afilter element 70, may be mounted to a fitting of the housing of a fluidtreatment assembly, such as a filter assembly (not shown), at the openend cap 73. The surface of the end cap and/or the core which contactsthe fitting may serve as the electrical contact which is coupled to aneutral potential such as ground through the housing. A fluid to betreated, e.g., filtered, is directed through the housing of the fluidtreatment assembly and preferably outside-in, but alternativelyinside-out, through the fluid treatment element, e.g., through a filterelement 70 in a dead-end mode of filtration. The fluid passes throughthe perforated cage 75 and is distributed by the upstream drainage layer80 along the upstream surface of the cushioning layer 81 and, hence, tothe upstream surface of the fluid treatment medium 82 or the fibrousmatrix 83. The fluid then passes through the fibrous matrix 83, wherethe fluid is treated, e.g., where undesirable substances such asparticulates are deposited on or within the fibrous matrix 83. The fluidthen passes through the conductive substrate 84, drains along thedownstream layer 85, and passes the perforated core 74 to the interiorof the core 74, from which the fluid exits the housing through the openend cap 73.

While not being bound to any particular theory of operation, it isbelieved that as the fluid passes the fibrous matrix 83, in particularas a conductive or nonconductive fluid passes through the fibrousmatrix, electrical charge may be transferred between the fibrous matrixand the fluid. By coupling the electrical contact 86 to the groundedfitting and by electrically connecting the conductive substrate 84 tothe electrical contact 86, e.g., via a conductive connection between theconductive substrate 84 and the conductive end cap 73, any electricalimbalance may be substantially offset and any charge build up in eitherthe fibrous matrix 83 or the fluid may be substantially inhibited.Because the fibrous matrix is laid on and bonded to the conductivesubstrate, the conductive substrate is particularly well coupledelectrically to the fibrous matrix, significantly enhancing the abilityof the conductive substrate to transfer charges between the fibrousmatrix and the electrical contact and hence the neutral potential.Consequently, fluid treatment elements embodying this third aspect ofthe invention are very effective at inhibiting charge build up in thefibrous matrix and/or the fluid.

While the embodiment illustrated in FIG. 4 has been described withreference to a generally cylindrical, fluid treatment element, such as apleated filter element arranged for dead-end filtration, the inventionis not limited to this embodiment. Many of the alternatives suggestedwith respect to the embodiments shown in FIGS. 1, 2, and 3 areapplicable to this embodiment. For example, the fluid treatment elementmay include a pleated pack and/or may be arranged for cross flowseparation or mass transfer, the fluid treatment element may include afluid treatment pack which is spirally-wound rather than pleated, and/orthe fluid treatment element may have a box-like configuration.

Another example of a fluid treatment element is a coalescer elementwhich accretes one phase of a fluid, e.g., a liquid discontinuous phase,in another phase of the fluid, e.g., a liquid or gas continuous phase,allowing the discontinuous phase to be separated from the continuousphase. International Publications No. WO 98/14257 and No. WO 97/38781and U.S. Pat. No. 5,443,724 and No. 5,480,547 disclose a variety ofcoalescer elements and coalescer assemblies, as well separator elementsand separator assemblies, and are incorporated herein by reference.

In accordance with another aspect of the invention, a fluid treatmentelement such as a coalescer element comprises first and secondconductive layers and a porous fluid treatment medium such as acoalescer medium. The first and second conductive layers are preferablyelectrically connected to each other and the coalescer medium isdisposed between them. As a fluid flows through the coalescer element,in particular, the coalescer medium, a discontinuous phase of the fluidis accreted on the surfaces of the coalescer medium. In addition, anelectrical charge may be transferred between the fluid and the coalescermedium. The first and second conductive layers are positioned insufficient proximity to the coalescer medium to offset any electricalimbalance, for example, by dissipating the charge and/or collecting thecharge in the coalescer medium and returning the charge to the fluid asit flows through the conductive layers or by preventing the charge fromaccumulating in the coalescer medium. Thus, even if the coalescerelement is electrically isolated from the ambient environment, e.g.,electrically isolated from a common or neutral potential such as ground,the first and/or second conductive layers may offset all or asubstantial portion of the electrical imbalance which may arise in thecoalescer medium. The coalescer medium is thus substantively surroundedby an electrical cage which offsets, e.g., reduces, inhibits, orprevents, the electrical imbalance.

As shown in FIG. 5, one example of a fluid treatment element such as acoalescer element 100 embodying the present invention has a hollowgenerally cylindrical configuration, and fluid flows outside-in or,preferably, inside-out through the coalescer element 100. The coalescerelement 100 may include a perforated conductive core 101 and a coalescermedium 102 disposed around the core 101. The coalescer medium 102preferably includes a packing material or coalescing matrix 103 having asmaller nominal pore size and a final classifier 104 having a largernominal pore size downstream of the coalescing matrix 103. The coalescermedium 102 thus has a graded nominal pore structure where an upstreamregion has a smaller nominal pore size than the nominal pore size of adownstream region. In the illustrated embodiment, a fluid preferablyflows inside-out through the coalescer element 100 and the coalescingmatrix 103 is disposed co-axially between the core 101 and the finalclassifier 104. A conductive wrap structure 105 having openings, such asthe wrap structure disclosed in International Publication No. WO98/14257, is preferably disposed around the final classifier 104. Eachof these components is preferably disposed between opposite end caps110, 111, one or both of which may be an opened end cap. The conductivecore 101 and the conductive wrap structure 105 may comprise the firstand second conductive layers with the coalescer medium 102 including thecoalescing matrix 103 disposed between them.

The core 101 may be fashioned from any suitably conductive material,such as a metal or a conductive polymer, or any non-conductive materialthat has been rendered conductive in any suitable manner and preferablyhas a perforated hollow configuration. For example, the core 101preferably comprises a hollow, perforated, stainless steel tube, wherefluid flows between the interior of the hollow tube and the exterior ofthe hollow tube via the perforations or holes. Alternatively, the coremay have a solid configuration or a hollow configuration without holesand flow channels may be disposed along the outer surface of the core.

The coalescer matrix 103 may be fashioned from a wide variety ofmaterials having suitable coalescing characteristics, including afibrous mass, fibrous mat, woven or non-woven sheets or screens, orporous membranes. The coalescing matrix 103 may be a single layerstructure or a multi-layer structure and may have a uniform porestructure or a graded pore structure where, for example, an upstreamregion adjacent to the core 101 has a larger pore size than a downstreamregion in order to more evenly distribute fluid flow from the core 101into the coalescing matrix 103. A graded pore structure may also beaffected with multiple layers where, for example, each layer has auniform pore structure and an upstream layer has a larger pore size thana downstream layer. However, the nominal pore size of the coalescingmatrix 103 is preferably in the range from about 0.2% or less to about20, or more, e.g., from about 0.2μ to about 5μ. Further, while thecoalescing matrix 103 may be pleated, it is preferably arranged in anon-pleated configuration, e.g., a hollow cylindrical configuration.

The coalescing matrix 103 may be formed from a material or may besurface modified in any suitable manner, e.g., coated with a material,which facilitates the formation of droplets of the discontinuous phaseand the accretion of these small droplets into larger droplets as thediscontinuous phase contacts the coalescing matrix 103. The desiredphysical and chemical characteristics, e.g., the critical surfaceenergy, of the coalescing matrix 103 which promotes the formation andaccretion of droplets of the discontinuous phase may vary in accordancewith the nature of the discontinuous phase and/or the continuous phase.Thus, the coalescing matrix 103, as well as the final classifier 104,may comprise a metallic material, a polymeric material, a glass fibermaterial, or any other suitable material or mixture of materials and maybe treated to modify its critical surface energy, e.g., by applicationof a suitable surface treatment, such a silicone or fluoropolymersurface treatment available from 3M Company or from Pall Corporation.

One embodiment of the coalescing matrix 103 may comprise a matrix ofnon-conductive polymeric fibers, e.g., polyester fibers, blown onto theperforated metal core 101, as described in International Publication No.WO 96/03194. The polymeric fibers of the coalescing matrix 103 may betreated to modify the critical surface energy by application of afluoropolymer surface treatment.

The final classifier 104 is disposed co-axially downstream of and,preferably, immediately adjacent to the coalescing matrix 103 andpreferably has a nominal pore size no less than and preferably greaterthan that of the coalescing matrix 103. For example, the nominal poresize of the final classifier 104 is preferably in the range from about50μ to about 1000μ, e.g., from about 50μ to about 300μ. The finalclassifier 104 may be fashioned from any suitable material or may besurface modified in any suitable manner, e.g., by application of afluoropolymer surface treatment, which facilitates drainage of thedroplets of the discontinuous phase away from the coalescing medium 103and/or which further facilitates the formation and the accretion ofdroplets of the discontinuous phase. The final classifier 104 is alsopreferably formed as a cylindrical mass or sheet of polymeric fibers,e.g., polyester fibers. In a preferred embodiment, the final classifier104 comprises a plurality of sheets of a fibrous polyester non-woven,e.g., about five sheets. The upstream sheet(s) have a smaller nominalpore size than the downstream sheet(s).

The conductive wrap structure 105 is disposed co-axially downstream ofthe final classifier 104, preferably immediately downstream. The wrapstructure 105 preferably comprises a porous material having holesextending through the porous material. The holes are preferably arrangeduniformly along the porous material and may have a dimension, such as adiameter, of about D, where D is any rational number in the range fromabout 20 thousandths of an inch or less to about 250 thousandths of aninch or more. The porous material may be treated to inhibit passage ofthe discontinuous phase but allow passage of the continuous phase.Accordingly, the droplets of the discontinuous phase may be constrainedto flow primarily through the holes of the wrap structure 105 while thecontinuous phase may pass through the pores of the porous material ofthe wrap structure 105.

The conductive wrap structure 105 may be formed from a conductivematerial, such as a metal, carbon, or a conductive polymer, or from anon-conductive material, such as glass fiber or a non-conductivepolymer, e.g., a non-conductive polymeric fiber, which is treated torender the wrap structure conductive. For example, the non-conductivematerial may be treated in any manner similar to those previouslymentioned with respect to the filter elements, including providing aconductive additive such as metal, carbon, or conductive polymericparticles or fibers within a non-conductive material or coating thenon-conductive material with a conductive coating such as a metal orcarbon coating.

The ends of the wrap structure 105, the final classifier 104, thecoalescing matrix 103, and the core 101 may be joined to opposite endcaps 110, 111 in any suitable manner, such as melt bonding, adhesivebonding, spin bonding, welding, or brazing. One of the end caps may beblind and the other may be open or both end caps may be open.

The conductive layers such as the conductive wrap 105 and the conductivecore 101 are preferably electrically connected to one another and may beelectrically connected to each other in a variety of ways. For example,they may be electrically connected in many of the same ways that theconductive layers of the filter packs and the filter elements previouslydiscussed are connected. For example, one of the conductive layers,e.g., the wrap structure 105, may physically contact the otherconductive layer, e.g., the conductive core 101, at the ends of theconductive layers adjacent to the end caps. Alternatively oradditionally, the first and second conductive layers may be electricallyconnected through the intervening layers. For example, the finalclassifier 104 and the coalescing matrix 103 may include conductivefibers including conductive filaments which electrically connect one ofthe conductive layers to the other conductive layer across the entirearea of the final classifier 104 and the coalescing matrix 103.Alternatively, or additionally, the first and second conductive layersmay be electrically coupled via a conductive end cap, e.g., a metal endcap or a conductive polymeric end cap, and/or via a conductive adhesiveat the end caps 110, 111. With the first and second conductive layerselectrically connected to each other, the fluid treatment medium such asthe coalescing medium 102 is substantively surrounded with an electricalcage.

While the embodiment illustrated in FIG. 5 has been described withreference to a fluid treatment element comprising a conductive core 101,a fluid treatment medium such as a coalescing medium 102 including acoalescing matrix 103 and a final classifier 104, and a conductive wrapstructure 105 arranged in a cylindrical configuration, the invention isnot limited to this embodiment. For example, one or more of the layers,such as the final classifier, may be eliminated entirely and/oradditional layers, such as a drainage layer between the coalescingmedium and the perforated core or a substrate on which the coalescingmatrix is laid, may be added. Further, the core may be non-conductive orit may be electrically isolated from the second conductive layer, andthe first conductive layer may comprise a conductive drainage layer or aconductive substrate. Further, the wrap structure may be non-conductiveor eliminated, and the second conductive layer may comprise a conductivefinal classifier, a conductive screen wrapped around the coalescingmatrix or a conductive outer retainer such as a metal cage or a metalscreen disposed around the exterior of the coalescer element.Additionally, the coalescer element may have a non-cylindrical geometry,e.g., a box-shaped configuration.

A fluid treatment element comprising the coalescer element 100 may beplaced in a housing (not shown) of a fluid treatment assembly comprisinga coalescer assembly or a combination coalescer and separator assembly.In one embodiment, the fluid treatment element includes an electricalcontact, and the first and second conductive layers preferably areelectrically connected to each other and are electrically coupled to theelectrical contact, which is arranged to be connected to a neutralpotential, e.g., ground. The first and second conductive layers may beelectrically coupled to the electrical contact and the electricalcontact may be electrically coupled to the neutral potential in anysuitable manner, for example, as previously discussed with respect tofilter elements.

In another embodiment, the first and second layers may be electricallyconnected to each other and isolated, e.g., insulated, from a common orneutral potential such as ground. The first and second conductive layersmay be isolated in any suitable manner, for example, as previouslydiscussed with respect to the filter elements.

In a preferred mode of operation, the fluid to be treated is directedthrough the housing of the fluid treatment assembly and through thefluid treatment element, e.g., inside out through coalescer element 100in a dead-end mode of coalescence. The fluid is distributed by theperforated conductive core 101 along the upstream surface of thecoalescing matrix 103. The fluid then passes through the fluid treatmentmedium, e.g., the coalescing matrix 103 and the final classifier 104,where droplets of the discontinuous phase are formed and accreted. Thedroplets of the discontinuous phase then pass through the holes of theconductive wrap structure 105 while the continuous phase passes throughthe porous material of the wrap structure 105.

While not being bound by any particular theory of operation, it isbelieved that as the fluid passes through the fluid treatment elementcomprising the coalescing element 100, in particular, as a conductive ornon-conductive fluid passes through the coalescer medium 102, electricalcharge may be transferred between the coalescer medium 102, e.g., thecoalescing matrix 103 and/or the final classifier 104, and the fluid.The first and second conductive layers comprising the perforatedconductive core 101 and the conductive wrap structure 105 are positionedin sufficiently close proximity to the fluid treatment medium, e.g., thecoalescing medium 102, to offset any electrical imbalance, e.g., togather the electrical charge from the coalescing matrix 103 and/or thefinal classifier 104 and dissipate the charge to ground or return thecharge to the fluid and/or to prevent the charge from accumulating inthe coalescing medium 102. For example, one or both of the first andsecond conductive layers may be immediately adjacent and in face-to-facecontact with the fluid treatment medium, e.g., the coalescing medium102. This configuration is preferred because it enhances the electricalcoupling between the coalescing medium 102 and the conductive layer(s)over the entire surface of the fluid treatment medium. Alternatively,one or more non-conductive layers may be interposed between the fluidtreatment medium and each of the first and second conductive layers ofthe coalescing element 100 as long as the first and/or second conductivelayers are sufficiently close to the fluid treatment medium to inhibitany electrical imbalance and/or charge build-up through the interveninglayer. The electrical imbalance and/or charge build-up in the fluidtreatment medium such as the coalescing medium 102 is thus substantiallyreduced.

While the embodiment illustrated in FIG. 5 has been described withreference to a generally cylindrical coalescer element 100 with a core101 permanently attached to the element 100, the invention is notlimited to this embodiment. For example, the conductive core may bepermanently attached to and electrically connected to the housing, andthe coalescer element may be removably mounted to the conductive core.The conductive core may be electrically connected to the otherconductive layer, e.g., the conductive wrap structure 105, in anysuitable manner. For example, the other conductive layer mayelectrically contact one or more conductive end caps and the conductiveend caps may physically contact the conductive core or may beelectrically connected to the core via a conductive spring, wire, strap,or a conductive seal such as a conductive O-ring. Alternatively, thecore may be non-conductive, and an inner conductive layer, such as aconductive drainage layer or substrate, may be disposed adjacent to thecoalescing medium and electrically coupled to the outer conductivelayer, e.g., via conductive end caps.

In accordance with another aspect of the invention, a fluid treatmentelement comprises one or more layers including a coalescer mediumarranged to form droplets of a discontinuous phase of a fluid flowingthrough the fluid treatment element. At least one of the layers of thefluid treatment element is conductive, and the fluid treatment elementfurther comprises an electrical contact which is electrically coupled tothe conductive layer of the fluid treatment element. The electricalcontact is arranged to be connected to a conductive portion of a fluidtreatment assembly, e.g., the housing of a coalescer assembly, which, inturn, is connected to a common or neutral potential such as ground. Asthe fluid flows through the fluid treatment assembly and, hence, throughthe fluid treatment element, the discontinuous phase of the fluid iscoalesced by the coalescing medium. In addition, an electrical chargemay be transferred between the fluid and the coalescing medium. Becausethe fluid treatment element includes a conductive layer coupled to aneutral potential via an electrical contact, any charge imbalance and/orbuild-up which may arise in the coalescer medium and/or the fluid can besubstantially offset, e.g., reduced or prevented, by the connection tothe neutral potential.

As shown in FIG. 6, one example of a fluid treatment element, e.g., acoalescer element 120, embodying the present invention comprises aperforated core 121, a coalescer medium 122, and a perforated wrapstructure 125 disposed between opposite end caps 130, 131. The coalescermedium 122 preferably includes a packing material or coalescing matrix123 and a final classifier 124. Each of the components of the coalescerelement 120 may be similar to the components of the coalescer element100 previously described.

However, in accordance with this aspect of the invention, one or more ofthe layers of the coalescer element 120 are conductive. For example, atleast one of the core 121, the coalescing matrix 123, the finalclassifier 124, and the perforated wrap structure 125 are conductive andcomprise the conductive layer of the fluid treatment. Any of theselayers may be formed from a conductive material or may be renderedconductive in a manner similar to those previously described whichrespect to the filter packs and the filter elements. In a preferredembodiment, the coalescing matrix 123 is blown onto a conductive,perforated, stainless steel core 121 and the conductive core 121comprises the only conductive layer of the fluid treatment element.Alternatively, the coalescing matrix or the final classifier or theperforated wrap structure may each comprise the sole conductive layer,or any two, three or four of the core, the coalescing matrix, the finalclassifier, and the perforated wrap may comprise conductive layers. Theconductive layer(s) is preferably in sufficiently close proximity to thecoalescing medium 122, e.g., the coalescing matrix 123, to gather theelectrical charge transferred between the fluid and the coalescingmedium 122. Preferably, the conductive layer is in face-to-face contactwith the coalescer medium 122 or matrix 123. While the coalescing mediumitself may be conductive or may be rendered conductive, the coalescingmedium is preferably fashioned in manner which enhances the physicaland/or chemical characteristics, e.g., critical surface energy, thatfacilitate coalescence and, therefore, the coalescing medium may benon-conductive.

The electrical contact, which may be similar to the electrical contactspreviously described for the filter elements, preferably comprises anyconductive portion of the fluid treatment element, e.g., the coalescerelement 120, which is electrically coupled to the conductive layer(s)and is arranged to contact a conductive portion of the fluid treatmentassembly, e.g., the housing of a coalescer assembly. For example, theelectrical contact may be a portion of the conductive core that iselectrically connected to a conductive portion of the housing, e.g., astool, a spider, or a tie rod of the housing. Alternatively oradditionally, the electrical contact may be a conductive portion of aconductive end cap that is electrically coupled to the conductivelayer(s) of the coalescer element, e.g., directly or via a conductivebonding agent, and to a conductive portion of the housing. Alternativelyor additionally, the electrical contact may comprise one or moreadditional conductive components such as a conductive wire, strap,spring or seal, e.g., a conductive O-ring or gasket, that iselectrically coupled to the coalescer medium via the conductive layer ofthe coalescer element, e.g., directly or via a conductive bonding agentand/or a conductive end cap, and to a conductive portion of the housing.Alternatively or additionally, the coalescer medium may be pleated andelectrical contact may comprise a conductive portion at the roots orcrests of the pleated coalescer medium or substrate that is electricallyconnected to the housing, e.g., to a conductive core or a conductivecage permanently connected to the housing.

As shown in FIG. 7, one example of a fluid treatment assembly, e.g., acoalescer assembly 140 includes a housing 141 having an inlet 142, anoutlet 143 and a tube sheet 144 including a plurality of stools 145. Acoalescer element 120 is mounted to a hub on each stool 145, forexample, by a tie rod 146 and a spider 147. The coalescer element 120includes a conductive core 121 electrically connected to oppositeconductive end caps 130, 131. A portion of the upper end cap 130 servesas the electrical contact electrically coupling the coalescer medium 122via the conductive core 121 to the tie rod 146 and, hence, to ground. Inaddition, a conductive O-ring 148 mounted to the lower end cap 131serves as the electrical contact electrically coupling the coalescermedium 122 via the conductive core 121 to the stool 145 and, hence, toground.

In a preferred mode of operation, the fluid to be treated is directedthrough the housing of the fluid treatment assembly and through thefluid treatment element, e.g., inside out through the coalescer element120 in a dead-end mode of coalescence. The fluid is distributed by theperforated conductive core 121 along the upstream surface of the fluidtreatment medium, e.g., the coalescer medium 122. The fluid then passesthrough the coalescer medium 122, e.g., the coalescing matrix 123 andthe final classifier 124, where droplets of the discontinuous phase areformed and accreted. The droplets of the discontinuous phase then passthrough the holes of the wrap structure 125 while the continuous phasepasses through the porous material of the wrap structure 125.

While not being bound by any particular theory of operation, it isbelieved that as the fluid passes through the fluid treatment elementcomprising the coalescing element 120, in particular, as a conductive ornon-conductive fluid passes through the coalescing medium 122,electrical charge may be transferred between the coalescer medium 122,e.g., the coalescing matrix 123 and/or the final classifier 124, andfluid. By coupling the electrical contact to the coalescer medium 122via the conductive layer of the coalescer element 120, e.g., theconductive core 121, and to the grounded housing, any charge imbalanceand any charge build-up in either the coalescer medium 122 or the fluidmay be substantially reduced or prevented entirely.

While the embodiment illustrated in FIG. 6 has been described withreference to a generally cylindrical coalescer element 120 having a core121 permanently mounted to the coalescer element 120, a coalescer matrix123, a final classifier 124, and a perforated wrap structure 125, theinvention is not limited to this embodiment. For example, the core maybe permanently attached to a housing and the coalescer may be removablymounted to the core. Further, one or more layers, such as the finalclassifier or the perforated wrap structure, may be eliminated entirelyand/or other conductive or non-conductive layers may be added, includinga drainage layer between the coalescing medium and the perforated core,a substrate on which the coalescing matrix is laid, a screen wrappedaround the downstream surface of the coalescing matrix, or an outerretainer, e.g., a cage or a screen disposed around the exterior of thecoalescer element. Additionally, the coalescer element may have anon-cylindrical geometry, e.g., a box-shaped configuration.

As shown in FIG. 8, another example of a fluid treatment elementincludes a coalescer element 150 disposed adjacent to and preferablydownstream of a filter element 151. The coalescer element 150 and thefilter element 151 may be fixably mounted adjacent to one anotherbetween opposite end caps 152, 153 or may be removably mounted asdisclosed, for example, in International Publication No. WO 96/33789 andU.S. Application No. 60/145,213, both of which are incorporated byreference. Both the coalescer element 150 and the filter element 151 mayinclude any of the previously described mechanisms for dissipating,transferring, and/or preventing the accumulation of electrical charge inthe fluid treatment medium.

Another example of a fluid treatment element is a separator elementwhich resists or prevents the passage of one phase of a fluid, e.g., aliquid discontinuous phase, but allows the passage of another phase,e.g., a liquid or gas continuous phase, through the separator element.In accordance with another aspect of the invention, a fluid treatmentelement such as a separator element comprises first and secondconductive layers and a porous fluid treatment medium such as aseparator medium. The first and second conductive layers are preferablyelectrically connected to each other and the separator medium isdisposed between them. The fluid is directed toward the separatorelement and the separator medium resists or prevents passage of thediscontinuous phase but allows passage of the continuous phase throughthe separator element. In addition, an electrical charge may betransferred between the fluid and the separator medium. The first andsecond conductive layers are positioned in sufficiently close proximityto the separator medium to offset any electrical imbalance, for example,by dissipating the charge and/or collecting the charge in the separatormedium and returning the charge to the fluid as it flows through theconductive layers or by preventing the charge from accumulating in theseparator medium. Thus, even if the separator element is electricallyisolated from the ambient environment, e.g., electrically isolated froma common or neutral potential such as ground, the first and/or secondconductive layers may offset all or a substantial portion of theelectrical imbalance which may arise in the separator medium. Theseparator medium is thus substantially surrounded by an electrical cagewhich offsets, e.g., reduces, inhibits or prevents, the electricalimbalance.

One example of a fluid treatment element such as a separator elementembodying the present invention has a hollow, generally cylindricalconfiguration and fluid flows inside-out or, preferably, outside-inthrough the separator element. The separator element preferablycomprises a perforated conductive core and an outer conductive mesh. Aseparator medium such as a single layer of a material which isliquiphobic with respect to the discontinuous phase and liquiphilic withrespect to the continuous phase is disposed between the perforated coreand the outer mesh. The outer mesh and the perforated core arepreferably electrically connected at the ends of the separator element,e.g., via direct physical contact or via conductive end caps or bondingagents.

While not being bound by any particular theory of operation, it isbelieved that as the continuous phase of a fluid passes through thefluid treatment element comprising the separator element, in particular,as a conductive or non-conductive fluid passes through a separatormedium, an electrical charge may be transferred between the separatormedium and the fluid. The first and second conductive layers comprisingthe perforated conductive core and the conductive outer sleeve arepositioned in sufficiently close proximity to the fluid treatmentmedium, e.g., the separator medium, to offset any electrical imbalance,e.g., to gather the electrical charge from the separator medium andreturn the charge to the fluid and/or to prevent the charge fromaccumulating in the separator medium.

In accordance with another aspect of the invention, a fluid treatmentelement comprises one or more layers including a separator mediumarranged to inhibit or prevent the passage of a discontinuous phasewhile allowing the passage of a continuous phase of a fluid. At leastone of the layers of the fluid treatment element is conductive, and thefluid treatment element further comprises an electrical contact which iselectrically coupled to the separator medium via the conductive layer ofthe fluid treatment element. The electrical contact is arranged to beconnected to a conductive portion of the fluid treatment assembly, e.g.,the housing of a separator assembly, which, in turn, is connected to acommon or neutral potential such as ground. As the continuous phaseflows through the fluid treatment assembly, and, hence, through theseparator medium, an electrical charge may be transferred between thefluid and the separator medium. Because the fluid treatment elementincludes a separator medium coupled to a neutral potential via theconductive layer and the electrical contact, any charge imbalance and/orbuild-up which may arise in the separator medium and/or the fluid can besubstantially offset by the connection to the neutral potential.

One example of a fluid treatment element, e.g., a separator elementembodying the present invention comprises a conductive perforated coreand a single layer of a separator medium disposed around the core andpreferably in intimate contact with the core. The separator medium maybe conductive or non-conductive. The ends of the conductive core and theseparator medium may be disposed between opposite end caps. Theelectrical contact, which may be similar to the electrical contactspreviously described with respect to the coalescer elements and thefilter elements, may be a portion of the conductive core that iselectrically connected to a conductive portion of the housing; theelectrical contact may be a conductive portion of a conductive end capthat is electrically coupled between the conductive core and theconductive portion of the housing; and/or the electrical contact may bean additional conductive component such as a conductive wire, strap,spring or seal, e.g., a conductive O-ring or gasket, that iselectrically coupled between the conductive core and a conductiveportion of the housing. As the continuous phase of the fluid flowsthrough the separator medium, any electrical charge imbalance and/orbuild-up in the separator medium is coupled to ground via the conductivecore and the electrical contact.

The conductive components of the present invention, including but notlimited to the conductive drainage layers, cushioning layers, fluidtreatment media, substrates and/or wrap members, as well as theconductive end caps, cage, core, seals, sealant and/or end cap bondingcomposition, preferably have high electrical conductivity or lowelectrical resistivity. For example, the conductive componentspreferably have a surface resistivity on the order of about 10¹⁰ohms/square or less, preferably on the order of about 10⁶ ohms/square orless, more preferably on the order of about 10⁴ ohms/square or less,e.g., from about 1×10³ ohms/square or less to about 7×10³ ohms/square ormore. Alternatively or additionally, the conductive componentspreferably have a resistivity on the order of about 10¹² ohm-centimetersor less, most preferably 10¹⁰ ohm-centimeters or less. The resistivityincluding the surface resistivity can be determined by methods known tothose skilled in the art, e.g., by ASTM Method D257 and/or D4496.

The various aspects of the invention have been described with respect tomany embodiments. However, the invention is not limited to theseembodiments. For example, one or more of the features of any of theseembodiments may be combined with one or more of the features of theother embodiments without departing from the scope of the invention.Further, one or more of the features of any of these embodiments may bemodified or omitted without departing from the scope of the invention.Accordingly, the various aspects of the invention include allmodifications encompassed within the spirit and scope of the inventionas defined by the following claims.

1. A fluid treatment element for substantially inhibiting an electricalcharge imbalance and/or a build-up of electrical charge, the fluidtreatment element comprising a multilayer composite including: anelectrically conductive fibrous matrix having a first side and a secondside, the electrically conductive fibrous matrix including a combinationof electrically conductive fibers and electrically nonconductive fibers,wherein the electrically conductive fibers of the electricallyconductive fibrous matrix substantially inhibit an electrical chargeimbalance and/or a build-up of electrical charge and includeelectrically conductive polymeric fibers, the electrically conductivefibers comprising less than about 50% by weight of the electricallyconductive fibrous matrix and having diameters of about 10 μm or less; aporous substrate for supporting the electrically conductive fibrousmatrix and having a first side and a second side, wherein the secondside of the electrically conductive fibrous matrix is disposed on thefirst side of the porous substrate; and a first drainage layerpositioned on one of the first side of the electrically conductivefibrous matrix and the second side of the porous substrate.
 2. The fluidtreatment element according to claim 1, wherein the electricallyconductive fibers comprise up to about 25% by the weight of theelectrically conductive fibrous matrix.
 3. The fluid treatment elementaccording to claim 1, wherein the electrically conductive fiberscomprise from about 15% to about 25% by weight of the electricallyconductive fibrous matrix.
 4. The fluid treatment element according toclaim 1, wherein the electrically conductive fibrous matrix includes abinder.
 5. The fluid treatment element according to claim 1, wherein theporous substrate is electrically conductive.
 6. The fluid treatmentelement according to claim 1, wherein the electrically nonconductivefibers include glass fibers, electrically nonconductive polymericfibers, or electrically nonconductive ceramic fibers.
 7. The fluidtreatment element according to claim 1, wherein the electricallyconductive fibrous matrix has a removal rating of about 25 μor less. 8.The fluid treatment element according to claim 1, further comprising acushioning layer having a first side and a second side, wherein thesecond side of the cushioning layer is positioned on and in contact withthe first side of the electrically conductive fibrous matrix, whereinthe first drainage layer has a first side and a second side, and whereinthe second side of the first drainage layer is positioned on and incontact with the first side of the cushioning layer.
 9. The fluidtreatment element according to claim 8, wherein the cushioning layer iselectrically conductive.
 10. The fluid treatment element according toclaim 1, wherein the multilayer composite is pleated.
 11. The fluidtreatment element according to claim 1, wherein the electricallyconductive fibers of the electrically conductive fibrous matrix havediameters of about 3 μm or less.
 12. The fluid treatment elementaccording to claim 1, wherein the electrically conductive fibers of theelectrically conductive fibrous matrix have diameters of about 1 μm orless.
 13. The fluid treatment element according to claim 1, wherein thefirst drainage layer is electrically conductive.
 14. The fluid treatmentelement according to claim 1, further comprising a second drainage layerpositioned on the second side of the porous substrate, wherein themultilayer composite is pleated.
 15. The fluid treatment elementaccording to claim 14, wherein the electrically conductive fibersinclude electrically conductive polymeric fibers which have diameters ofabout 1 μm or less.
 16. The fluid treatment element according to claim15, wherein the electrically conductive fibrous matrix and the poroussubstrate together form a filter medium.
 17. The fluid treatment elementaccording to claim 1, wherein the electrically conductive fibrous matrixand the porous substrate together form a filter medium.
 18. The fluidtreatment element according to claim 1, wherein the electricallynon-conductive fibers include glass fibers.